The present invention relates to a process for the production of a mushroom flavouring by addition of a cell-wall-macerating enzyme composition to a mushroom preparation.
Edible fungi are important flavouring additives in many dishes and are raw materials which are widely used particularly in nutritionally conscious cuisine. They are distinguished by a low content of digestible carbohydrates and fat, and in contrast have a considerable protein content and a significant amount of unusual glucan dietary fibres. In recent decades it has become possible to culture the edible fungi most frequently used (common cultivated mushrooms, oyster mushrooms, shiitake, Boletus lutens and China mushrooms). One of the mushrooms which are being much used because of their unique taste/aroma is the dried cep (Boletus edulis). The cep is a symbiotic fungus and still cannot be successfully cultured. It is available as a gathered natural raw material only in fluctuating amounts and quality. The fresh Boletus edulis occurs as mycorrhiza in association with certain types of tree only in forests and is air-dried after harvesting, as a result of which it only then develops its typical spicy flavour. Dried cep contains approximately 20% protein, 3 to 4% fat and only 4% digestible carbohydrates, the rest is indigestible dietary fibre and about 6% minerals. In addition, a significant amount of purines is present.
In addition to truffles and chanterelles, the cep is the most expensive edible fungus which cannot be cultured and for which there is simultaneously a high demand. For industrial use, for example in mushroom dishes, processed products (slices, granules and powder) are used which are freed from foreign matter and sand. One difficulty in the processing of cep is that the material is supplied with a variable water content and is contaminated, inter alia, by sand particles. This is the reason why in industrial processing a residue is always produced which cannot be utilized further. This residue, however, still contains the complete flavour potential which could be utilized after digestion of the fungal cells to produce flavour substances. The flavour substances which can be detected in fungi, particularly Boletus edulis, are highly basic amino acids, pyrazines, alcohols, phenols and amines, and, as volatile compounds, lactones and sulphur compounds and 1-octen-3-ol which is typical of fresh mushrooms and 1-octen-3-one which is typical of cooked mushrooms.
Fungal cell walls principally consist of a framework substance (chitin) embedded in a protein and carbohydrate matrix. Chitin is a poorly degradable, nitrogen-containing cellulose derivative (N-acetyl-D-glucosamine homopolymer, 2-acetamidocellulose). In common cultivated mushrooms, chitin microfibres are embedded in a xcex2-1,3-glucan matrix.
A number of processes are known in the prior art for producing extracts or flavour compounds from edible fungi.
It is known to produce a natural common cultivated mushroom flavour by concentrating mushroom cooking water (Wu et al., 1981, in: The Quality of Food and Beverages: Chemistry and Technology, Vol. I, pages 133 to 145). This route is not possible for producing flavour from dried mushrooms.
DE 35 24 473 discloses the production of a natural mushroom juice by removing juice from mushroom fruiting bodies, flavour enrichment being achieved by evaporation under vacuum.
FR 2 357 191 discloses a process for production of mushroom extract by aqueous maceration and subsequent pressing of the extract and sterilization.
EP 288 773 describes, as a method for enriching a mushroom flavouring, preferably from homogenized mushrooms, a fermentation with the flavour precursor linolenic acid.
EP 600 684 B1 discloses a method for producing flavoured yeast extracts using hydrolysates of fruit, vegetable, herbs, spices and/or fungi. These hydrolysates may be formed enzymatically. Suitable enzymes for the enzymatic hydrolysis include carbohydrases, in particular cellulases, hemi-cellulases, pectinases and endogalacturonases.
Food Engineering, 1988, 60 (11) 53, 56 describes for shiitake, the production of a flavour after aqueous and alcoholic extraction.
A number of cep powders which have been used for flavouring also have, in addition to the sand content, the disadvantage of a restricted storage life due to enzyme activities which are still present, for example lipases. The conventional processes for the production of mushroom flavour frequently have the disadvantage that either many aroma compounds and flavour substances are destroyed due to harsh conditions, or that under milder conditions the yield, based on the fungal material used, is low, since the desired substances can only be isolated inadequately from the fungal cells.
An object of the present invention is to provide a process for the production of a mushroom flavouring which firstly has a good yield and secondly produces a natural mushroom flavour which includes the important hydrophilic flavour potential (aroma, proteins, taste-active nucleotides).
Surprisingly, it has been found that a typical hydrophilic mushroom flavour can be produced from mushrooms by a specific enzymatic digestion. According to the process of the invention, an edible fungus preparation is firstly prepared. A cell-wall-macerating enzyme composition exhibiting chitinase activity and/or mutanase activity is then allowed to act on this edible fungus preparation. Finally, if appropriate, solid constituents are separated off.